Electric coil and transformer and process for making same



June 10, 1930. H. H. WERMINE ELECTRIC COIL AND TRANSFORMER AND PROCESSFOR MAKING SAME Filed April 2, 1927 Patented June 10, 1930 UNITED STATESPATENT OFFICE HUGO H. WEBMINE, OI VILLA PARK, ILLINOIS, ASSIGNOR TOBELDEN.. MANUFAC- TURING COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OFILLINOIS ELECTRIC COIL AND TRANSFORMER AND PROCESS FOR MAKING SAMEApplication filed April 2, 1927.

.tective casing preferably of insulating material impervious tomoisture.

Anotherlobject is to provide an improved process and an improved mode ofconstruction by which a weather proof casing may be molded around anelectric coil of the described class without impairing the mechanicalproperties or electrical characteristics of the winding. Another objectis to provide improved means for connecting the winding with an externalcircuit.

Other objects are to provide a coil structure of relatively few andsimple parts which may be manufactured rapidly and economi cally andwhich will be stron and durable so as to be capable of withstan ingrough handling, to which devices of this kind are sometimes subjected,and in general, to provide an improved coil structure of the characterindicated.

I Other objects and advantages of the invention will become apparent byreference to the following specification and accompanying drawingillustrating a telephone transformer made in accordance with a selectedembodiment of my invention, and in which drawmg:

Fig. 1 is a perspective of the finished transformer.

Fig. 2 is a section on the line 22 of Fig. 1.

Fig. 3 is a perspective of the bobbin on which the transformer windingsare wound.

Fig. 4 is a perspective of one of the elements used in forming the core,and

Fig. 5 is a perspective of a shielding element consisting of two parts,the parts being shown separated.

The transformer herein disclosed comprises a metal core 10, a bobbin11," primary and secondary windings 12 and 13 respectively, a shield 14,an outer shell or casing 15 and bind ing posts 16. The core 10 ispreferably laminated, being made up of a plurality of suit- Serial No.180,356.

able iron plates 17 such as illustrated in Fig. 4. The plates 17 areapertured as indicated at 1818 through which apertures the windings andbobbin passes, as will be hereinafter described, and the plate isslitted as indicated at 1919 for a purpose which will be hereinafterbrought out.

The bobbin is preferably a moulded member made up of insulatingmaterial, and com prises a tubular body portion 20 having laterallyextending flanges 21-21 adjacent its ends. The primary and secondarywindings 12 and 13 respectively, are wound about the body portion 20between the end flanges 2l-21 whereby they are retained on the bodyportion, and binding posts indicated at 16 are provided for receivingthe terminals of the said coils or windings 12 and 13. The primary andsecondary windings are preferably separated by a layer of suitableinsulating material such as empire cloth indicated at 34 in Fig. 2, andthe outer surface of the secondary winding is preferably covered with awrapping of heat resisting insulating material such as mica, asindicated at 35. Apertures 22 and 23 are provided in one of the flanges21 for the purpose of permitting the terminals of the primary coil to beextended from between the flanges 21 to the outside of the bobbin tofacilitate electrical connection thereof to adjacent binding posts 1616.Suitable apertures 24 and 25 are also provided in the same flange forpermitting the passage of the terminals of the secondary winding frombetween the flanges to'the outsideof the bobbin and to facilitateelectrical connection thereof to the adjacent binding post 16.

The binding posts 16 preferably comprise metal members provided withscrew threading as indicated at 26 and knurling at their lower ends, asindicated at 27. The binding posts are permanently mounted on the bobbinby being moulded in place in one of the end flanges, the knurlingfacilitating secure holding of the posts by the material of the flange.

The binding posts are preferably set up from the inside of the flange asindicated at 28 (Fig. 2) so as to prevent any possible undesirablecontacting between the end of the binding post and the coils or windings12 and 13, and the flange on which the binding posts are mounted ispreferably provided with upstanding bosses as indicated at 29 around therespective binding posts so as to strengthen the flange in the vicinityof the post. The terminals of the coils are extended through theapertures 22, 23, 24 and 25 as above described, and are respectivelyconnected to the binding posts by being bared and wound around the postat its base as best shown in Fig. 2. A spring Washer is presseddownwardly over the post so as to tightly clamp the wire against theface of the bosses 29 and is retained in such position by. the screwthreading 26 as will be readily understood from an inspection of Fig. 2.The spring Washer 30 is effective to insure the establishw The coreplates 17 are assembled one by one to form the complete core 10 byflexing.

the ends 31 and 32 out of alignment with the central portion 33, theslits 1919 permitting this, and the central portion 33 being then passedthrough the tubular body portion 20 of the bobbin. A sufficient numberof these plates 17 are so assembled on the bobbin to, form a tightlypacked complete core as indicated at 10 in Fig. 2.

The shield 14 comprises a pair of metal members as indicated in Fig. 5,whereinthe members are shown separated and the upper member is indicatedat 36, and the lower member at 37. These members are shaped to fitsnugly about the upper and lower portions respectively of the assembledcore and winding carrying bobbin 11. The lower section 37 of the shieldis provided with an off- I set flange 38 whichfits over the lowermarginal portion of the upper section 36* as clearly shown in Fig. 2 soas to properly align the sections. The upper section 36 is provided withrelatively large apertures 3939 which pass freely over the respectivebinding posts 16 and spring washers 30 so as to avoid making electricalcontact therewith. Another aperture 40 of smaller diameter is providedin the upper section 36 of the shield, and is adapted to fit rathersnugly .about one of the binding posts 16 and to overly the sprin washer30 on the post so as to establish goo electrical connection therewith.It is contemplated that the small aperture 40 will be provided so as tocontact with the one of the binding posts 16 which in the majority ofradio receiving sets is grounded, and the shield will therefore beeffective to prevent disturbance of or interference with the action ofthe transformer byoutside electrical forces.

The casing 15 is preferabl made up of insulating material such as baelite or the like, and itv may conveniently be made of semicuredbakelite which is somewhat pliable and flexible, and capable of beingpressed into the desired shape. In the present instance I make thecasing 15 by first forming a recess in a sheet of semi-cured materialintroduced into the mold, which recesswill be shaped so as to snuglyreceive an upper portion of the inverted transformer structure, with thebinding posts 16 projecting therethrough. When the transformer structurehas been positioned in the bakelite-lined recess of the mold a furthersupply of the material is disposed about the lower portion of thetransformer, and then the die is closed and pressure and heat applied inthe usual manner. To save material there may be formed side channels asindicated at 4141. The flange 42 which consists of an integral part ofthe casing serves as a base or mounting by which the transformer may besecured in position.

It will. be readily understood that there is thus produced a unitarycasing of solid impervious bakelite completely surrounding thetransformer and permanently protecting the same from externaldeleterious agencies.

It will be manifest that powdered bakelite or analogous material may beemployed instead of or in conjunction with the semi-cured sheet as abovedescribed. In the present instance it will be observed that the shield14 when made of metal serves as a barrier for electrical inductiveeffects. Also, of whatever material it may be made, it has theadditional functions of preventing bakelite from being forced into theinterstices of the winding during the molding and curing operation andof protecting the winding from the heavy pressure necessarily employedin the described process.

The term bakelite as used herein means any kilpd of phenol condensationproduct or the 11 e.

A casing such as above described, may be made in other ways than thatwhich I have just described, and I am aware that other I changes in theform, construction, and arrangement of parts may be made withoutdeparting from the spirit of the invention, the scope ofwhich should bedetermined by reference to the following claims which should beconstrued as broadly as possible consistent with the state'of the art.

I claim as my invention:

1. In a transformer of the class described, the combination of a bobbin,primary andsecondary coils wound on said bobbin, :1- plurality ofbinding posts permanently mounted on said bobbin and connectedrespectively to the terminals of said coils, a metallic shield enclosingsaid bobbin and said coils, said shield being apertured to permitsaid'binding posts to project outwardly .therethrough and electricallyconnected to one of said posts but 'not to the others, and a casing ofimpervio'us material enclosing said shield.

2. In a transformer of the class described, the combination of a bobbin,primary and secondary coils wound on said bobbin, and having theirrespective terminals extending outwardly therefrom, a metallic shieldenclosing said windings and connected to one of said terminals but notto the others, and a hermetically sealed casing of impervious insulatingmaterial enclosing said shield, said terminals projecting outwardlythrough said shield and casing for permitting connection of electricconductors thereto.

3. In a transformer of the class described, the combination of a bobbinhaving a tubu lar body portion and a pair of spaced flanges projectinglaterally therefrom, a primary and a secondary coil wound on saidtubular portion between said flanges, a plurality of binding postsfixedly mounted on one of said flanges and connected respectively to theterminals of said coils, a metallic shield enclosing said core, bobbinand coils, said shield being apertured to permit said binding posts toproject therethrough, and a one-piece casing of impervious insulatingmaterial over said shield.

4. In a transformer of the class described,

the combination of a bobbin having a tubular body portion and a pair ofspaced flanges projecting laterally therefrom, a primary and a secondarycoil wound on said tubular portion between said flanges, a plurality ofbinding posts fixedly mounted on one of said flanges and connectedrespectively to the terminals of said coils, a two-part metallic shieldenclosing said core, and electrically connected to one of said bindingposts, said shield comprising a lower part and an upper part, said upperpart having a plurality of apertules'for permitting said binding poststo project therethrough and one of said parts being provided with meansfor maintaining the other part in alignment therewith, and a one-piececasing of impervious insulating material enclosing said shield.

In an electric coil construction, the combination of a winding, a shleldsurrounding said winding, and a one piece casing of insulating materialmolded around and envelop mg said parts and constituting a hermeticseal. therefor.

6 In an electric coil construction, the com bination of a bobbin, awinding thereon, a shield around said bobbin and winding, and aone-piece casing of insulating material molded around and envelopingsaid parts and consl'ituting a hermetic seal therefor.

T, In an electric coil construction, the combination of a bobbin, awinding thereon, a shield around said bobbin and winding, and a onepiece casing of insulating material, molded around and enveloping saidparts, said casing constituting a hermetic seal for said parts and asupporting base for the coil.

8. In an electric coil construction of the class described, thecombination of a winding, an impervious one-piece insulating shellenclosing said winding, connectors for said winding rigidly mounted onsaid winding and projecting outwardly through said shell, and means forpreventing the casing material from entering the interstices of thewinding during the molding process.

9. In an electric coil construction, the combination of a winding,'asupport for said winding, a one-piece rigid insulating shell moldedaround said winding and support and hermetically sealing the same, aconnector for said coil supported by said support and extendingoutwardly through said shell, and a protective shield interposed betweensaid shell and winding.

' HUGO H. IVER-MINE.

